High Frequency AC Research Articles

A Comprehensive Review of High-Frequency AC Microgrids for Distribution Systems

A Comprehensive Review of High-Frequency AC Microgrids for Distribution Systems

Magnetic Memory Effects in BaFe2(As0.68P0.32)2 Superconducting Single Crystal.

Among many iron-based superconductors, isovalently substituted BaFe2(As1-xPx)2 displays, for x ≈ 0.3, apart from the quite usual Second Magnetization Peak (SMP) in the field dependence of the critical current density, an unusual peak effect in the temperature dependence of the critical current density in the constant field, which is related to the rhombic-to-square (RST) structural transition of the Bragg vortex glass (BVG). By using multi-harmonic AC susceptibility investigations in three different cooling regimes-field cooling, zero-field cooling, and field cooling with measurements during warming up-we have discovered the existence of a temperature region in which there is a pronounced magnetic memory effect, which we attributed to the direction of the structural transition. The observed huge differences in the third harmonic susceptibility at low and high AC frequencies indicates the difference in the time-scale of the structural transition in comparison with the timescale of the vortex excitations. Our findings show that the RST influence on the vortex dynamics goes beyond the previously observed influence on the onset of the SMP.

Dynamic permittivity of confined water under a static background field.

Molecular and collective reorientations in interfacial water are by-and-large decelerated near surfaces subjected to outgoing electric fields (pointing from surface to liquid, i.e., when the surface carries positive charge). In incoming fields at negatively charged surfaces, these rates show a nonmonotonic dependence on field strength where fastest reorientations are observed when the field alignment barely offsets the polarizing effects due to interfacial hydrogen bonding. This extremum coincides with a peak of local static permittivity. We use molecular dynamics simulations to explore the impact of background static field on high frequency AC permittivity in hydration water under an electric field mimicking the conditions inside a capacitor where one of the confinement walls is subject to an outgoing field and the other one to an incoming field. At strong static fields, the absorption peak undergoes a monotonic blue shift upon increasing field strength in both hydration layers. At intermediate fields, however, the hydration region at the wall under an incoming field (the negative capacitor plate) features a red shift coinciding with maximal static-permittivity and reorientation-rate. The shift is mostly determined by the variation of the inverse static dielectric constant as proposed for mono-exponentially decaying polarization correlations. Conversely, hydration water at the opposite (positively charged) surface features a monotonic blue shift consistent with conventional saturation. The sensitivity of absorption peaks on the field suggests that surface charge densities could be deduced from sub-THz dielectric spectroscopy experiments in porous materials when interfaces accommodate a major fraction of water contained in the system.

Analysis and Control of a Three-Port Converter With High-Frequency AC Link for Hybrid Unmanned/Autonomous Aerial Vehicles

Analysis and Control of a Three-Port Converter With High-Frequency AC Link for Hybrid Unmanned/Autonomous Aerial Vehicles

In Situ Time-Resolved Atomic-Scale Response of 2D TMD WSe2 under High-Frequency AC Electric Fields

In Situ Time-Resolved Atomic-Scale Response of 2D TMD WSe2 under High-Frequency AC Electric Fields

New Mini Neutron Tubes with Multiple Applications

Recent experimental investigations have demonstrated that a substantial amount of H−/D− ions can be formed by thermal desorption processes. Based on these new findings, new mini axial and coaxial-type neutron tubes have been developed for the production of high or low-energy neutrons via the d-d, d-10B, d-7Li or p-7Li nuclear reactions. By operating these mini neutron tubes with a high frequency AC high-voltage supply, short pulses of high intensity neutron beams can be generated. Multiple applications, such as carbon and well logging, neutron imaging, cancer therapy, medical isotope production, fission reactor start-up, fusion reactor material evaluation, homeland security and space exploration can be performed with the subcompact neutron generator system. It is shown that the performance of these new mini neutron tubes can exceed those of the conventional plasma-based neutron sources.

Improvement of AC Conditioning Effect in Vacuum by High Frequency Voltage

To improve the dielectric strength in vacuum, spark conditioning through repetitive breakdowns by AC or impulse voltage is an effective method. AC conditioning at commercial power frequencies has been widely used due to its cost‐effectiveness, but the breakdown voltage after AC conditioning is generally lower compared to impulse conditioning. We have confirmed that multiple breakdowns occur successively in a half cycle of AC voltage application. It is considered that the multiple breakdowns are harmful for conditioning and triggered due to the previous breakdown in the same half cycle. In this paper, we discuss dielectric strength improvement by high frequency AC conditioning and how the multiple breakdowns are induced. We experimentally confirmed that the AC conditioning effect is improved by increasing the frequency of AC voltage for different applied AC conditioning voltages in a sphere‐plane electrode system. We focused on the breakdown position from the light emission images during AC conditioning to investigate whether the multiple breakdowns were induced or affected by the previous breakdown. We found that the multiple breakdowns occurred close to the previous breakdown position. The multiple breakdowns would be induced by the collision of metal particles due to the previous breakdown with the counter electrode. These breakdowns do not contribute to removing protrusion and would lead to damage to the electrode surface. The increasing frequency of AC conditioning would suppress the multiple breakdowns and improve the dielectric strength in vacuum. © 2024 The Author(s). IEEJ Transactions on Electrical and Electronic Engineering published by Institute of Electrical Engineers of Japan and Wiley Periodicals LLC.

Single-Stage LLC Resonant Converter for Induction Heating System with Improved Power Quality

This paper proposes a single-stage direct AC to high-frequency (HF) AC resonant converter based on LLC configuration for induction heating (IH) systems or HF applications. Unlike conventional converters for IH systems, the proposed topology converts the utility frequency to HF AC in a single stage without using a DC link inductor and capacitors and takes the advantages of LLC configuration. Additionally, it improves the power factor to 0.9–1, lowers the THD (3.2% experimentally), and protects against the high-frequency components. An embedded control scheme was designed to keep the HF current oscillating at a resonant frequency, ensuring zero-voltage switching. The operating principle of the proposed topology was investigated using mathematical equations and equivalent circuits. Finally, it was verified using computer simulation, and an experimental prototype of 1.1 kW was developed to demonstrate the proposed topology’s uniqueness.

A Multimode Power Processor With Wired and Wireless Battery Charging for Electric Vehicle

The propulsion unit is the prime power module in an Electric Vehicle (EV) that keeps it moving. This module includes a propulsion motor and a power electronic interface that converts DC to three phase AC for driving the motor. In addition to this, separate power electronic modules are used for on-board wired charging and wireless charging. This paper proposes a multimode power processor for EV capable of serving the purpose of three different power modules required for propulsion, wired charging and wireless charging. This optimizes the weight, volume, and cost of the EV as separate power modules are avoided for three different modes. This paper also proposes a new scheme for the transmitting side power electronic module that taps power from the single-phase utility grid and generates high frequency AC using a resonant inverter for wireless power transfer. In both the wired and wireless charging method, the proposed technique draws power from the single-phase wall outlet, charges the EV battery pack with constant current-constant voltage (CC-CV) charging logic and performs power factor correction operation at the input AC grid side. A laboratory scale prototype is developed for experimentally validating the proposed concept with a 24 V, 30 Ah battery set and a 24 V, 400 W BLDC motor.

Solar Induction Cooker

There is no available power grid in the rural areas in many countries in South America, Asia and Africa. st places, Fossil fuel or wood is used for cooking. Besides environmental issues, fossil fuel and wood from trees are being depleted at a fast rate. Solar power is available everywhere during day time in all countries. This solar induction cooker uses a solar panel, which gives a variable dc, to charge a battery. The dc from the battery is converted to a high frequency ac voltage by an inverter circuit. This inverter circuit supplies alternating current to a coil on a magnetic core where alternating flux is produced. This alternating flux produces in the magnetic core Eddy current and Hysteresis ‘losses’ inside the magnetic core. In this application, these losses will produce useful heat. A cooking pot placed on the magnetic core will be used for cooking.

Effective High Frequency AC Conditioning in Vacuum

Effective High Frequency AC Conditioning in Vacuum

Analysis of Electrical Aging Effects on AC High Frequency Motor Based on Exchange Market Algorithm Model Parameter Identification

Analysis of Electrical Aging Effects on AC High Frequency Motor Based on Exchange Market Algorithm Model Parameter Identification

A novel generalized multi input boosting multi-level inverter (MIB-MLI) for high-frequency AC (HFAC) power distribution

The simplified topology for the high-frequency ac (HFAC) power distribution method with a multi-level inverter (MLI) hybrid switched capacitor (SC) is introduced. Capacitors, switches, diodes, and DC sources are among the components that are reduced in the designed MIB-MLI (Multi Input Boosting Multi-level Inverter). Where asymmetric dc voltage sources are available, such as in renewable energy farm-based ac microgrids and current electric vehicle, this architecture is advantageous. The proposed inverter has the feature of self-balancing the capacitor voltages and voltage boosting by using the series-parallel conversion scheme. The quality of output power is increased when a dc source array is connected with the unidirectional switched converter. Moreover, if a major phase variation betwixt the output current along with the voltage is no more mandatory, multiple alive switches may be recouped with diodes. In the switched capacitor group ripple volatge is reciprocal to the output frequency, so the MIB-MLI is favorable for HFAC implementations. Also, this paper clarifies the operating theory of the complete network and switching condition covered by the sinusoidal pulse width modulation (SPWM) technique. Mathematical equation related to power loss and capacitor voltages are provided. The modeling and simulation results of the proposed seventeen-level (17-L) inverter are depicted in this paper. The findings have shown that the proposed inverter is superior at HFAC along with the power efficiency of the inverter is adequate with SPWM technique.

Load and Coupling Variations Analysis of Capacitive Power Transfer at 6.78MHz Operating Frequency for Biomedical Implantable Device

This paper presents the design and analysis of load and coupling variations for a current Wireless Power Transfer (WPT) technique, known as Capacitive Power Transfer (CPT). Due to its strength, CPT becomes an effective and essential alternative to conservative technique, which is Inductive Power Transfer (IPT). It can compete IPT in industrial demand since it has a small number of component usage, uncomplicated topology, increases electromagnetic interference (EMI) shielding performance and robust to surrounding metallic elements. Class E power amplifier with the presence of π1b matching resonant circuit is applied in this work as a high frequency ac power source since it has the ability to perform dc-to-ac inversion efficiently. It supports the CPT system to attain a maximum power transmission. MATLAB software is used to design and simulate the CPT circuit; and the analysis is made up from the results. This proposed system able to generate 1W of output power by maintaining up to 98% efficiency at 6.78MHz operating frequency for Biomedical Implantable Device application. The analysis of load variation is in the range of 50Ω until 1kΩ; meanwhile for coupling variation is between 1mm to 15mm.

Design Consideration and Conductor Selection of a Low AC Loss HTS REBCO Magnet Carrying High Currents at 20 K and 40 K

AC loss in high temperature superconductor coils have been frequently studied, however, mostly for AC power ap-plications at 77 K, rather than specifically for high current but low frequency AC superconducting magnet at 20-40 K. Due to their easy operation and Helium shortage, more HTS magnet systems employ conduction-cooling with cryocoolers. The HTS magnets are known for high stability and likely tolerate high AC loss, but it is unclear what is the maximum AC frequency assuming that cry-ocooler has limited capability (a few hundred Watts) for the 20-40 K temperature range. This paper will specifically study AC loss in a simple HTS dipole but with three conductor/cable options using simulations, (1) 12 mm wide tape, (2) two parallel 6 mm wide tapes, and (3) 6/2 (six 2 mm strands) Roebel cables. It has been found that the magnet at 5 Hz generates 200 – 400 W AC loss at 20 K or 40 K, potentially be cooled by two single stage cryocoolers. The 6/2 Roe-bel cable based magnet may allow higher frequency (6-8 Hz) due to its transposition and narrower conductor width.

Artificial Intelligence Approach for the Control of SPMSG Based Grid Connected WECS

In India, power plant requirement is rapidly increasing as non-conventional sources are in current need. Government financial aid plays important role for generator plant execution because of its tedious procedure. If the utilization of wind power production has to be doubled, then machines, turbines and converters are essential in two numbers. The research work includes parallel connection of two machines using star-delta-star transformer fashion resulting in six-phase permanent synchronous machine. This arrangement is more economical as the number of converters are reduced thereby increasing the efficiency by minimizing the switching losses. Initially rectifier setup is used wherein high frequency AC is converted to low frequency and maximum power point tracking is done with the aid of a converter. It is DC-DC conversion by decoupled DQ strategy. Later, it is again converted back to three phase AC so as to synchronize it to the grid. The system response is analysed by conventional PI controller by reducing the noise in the real & reactive power generation. Further, ANFIS-PI controller is implemented to improve the response of PI controller which is much essential for wind power generation. The MATLAB simulated results of PI controller system response and ANFIS-PI controller is presented in this paper.

Single-Phase Wireless Electric Vehicle Charger Using EF2 Inverter

This paper proposes a wireless battery charger topology for electric vehicle (EV) application that can be installed in public charging infrastructure as well as in home premises. The proposed topology can maintain constant current as well as constant voltage at the battery terminal and simultaneously can maintain near unity power factor at the input side using power factor correction (PFC) operation and thus satisfy all the criteria of a standard EV charger. The heart of the wireless power transfer (WPT) scheme is a high-frequency (HF) inverter. In this work, a class EF2 inverter is used to generate HF AC in such a way that it can deliver power with variable loading condition while maintaining constant current (CC) or constant voltage (CV) according to the requirement of CC-CV charging profile. To supply power to this EF2 inverter, an AC-DC front-end converter (stage-1) is integrated with the charger. The stage-1 is operated as a constant voltage source to the EF2 inverter for CC mode and constant current source for CV mode operation. CC-CV at the battery end and PFC at the input end are achieved only by controlling the gate pulse of stage-1. The WPT coils are first simulated using Ansys Maxwell package, and the complete charger is simulated with PSIM simulation software. A scaled-down 200 W laboratory prototype of the proposed charger is developed and tested with a resistive load to validate the idea. The wireless power transfer is achieved for a maximum distance of 12 cm between the transmitting and receiving coil. Finally, the charger is tested to charge both 12 V and 24 V battery packs and the CC-CV charging profile is presented for the 24 V, 30 Ah battery pack.

Multi–Port High–Frequency AC–Link and Indirect Matrix Converters: A Generalized Structure

Multi–Port High–Frequency AC–Link and Indirect Matrix Converters: A Generalized Structure

Investigation on growth, structural and physico-chemical traits of 4-N, N-dimethylamino-4′-N'-phenyl-stilbazolium hexafluorophosphate (DAPSH) crystal

An organic salt 4-N,N-dimethylamino-4′-N’-phenyl-stilbazolium hexafluorophospate (DAPSH) was synthesized by metathesization process using acetonitrile solvent and DAPSH was crystallized by slow evaporation method. Single crystal X-ray diffraction (SXRD) analysis of DAPSH crystal revealed that the crystal possesses monoclinic crystal system with the non-centrosymmetric space group Cc. The existence of various functional groups present in the titular material is affirmed using FTIR analysis. UV–vis-NIR spectral analysis revealed the optical absorption of DAPSH crystal and the band gap as 3.1 eV. The elemental percentage composition was verified by CHN and EDAX analysis. Vickers Microhardness testing was used to assess the mechanical stability of the produced crystal. The DAPSH crystal is stable up to 250 °C, according to thermal analysis. The Kurtz and Perry NLO test confirms DAPSH's second harmonic generation (SHG) ability. The dielectric measurement was conducted in the frequency range from 50 Hz to 5 MHz for different temperatures (313, 323, 373, 423 and 473 K). The crystal exhibited low dielectric loss in the high frequency region and AC conductivity was calculated from the dielectric data. The anticancer and toxicity properties of the produced DAPSH crystal were investigated and it was confirmed to be an effective substance against cancer cells.

Indoor Solar Based Cooking Stove with Storage

An induction cooker fed from a renewable source of energy like solar. Many people in the flourishing areas of the world struggle to cook with stoves that emit hazardous fumes and contribute to green- house gas emission; Induction cooking is derived from the principle of electromagnetic induction by inducing eddy currents in the coil that get excited in the ferromagnetic material to cause heating.Solar Powered Induction Cooker uses solar (polycrystalline pvmodule)as a source of energy. The overall setup is done in two stages, one is Dc to Dc converter stage and the other one is conversion of boosted Dc to high frequency Ac. Dc to Dc converter is required for boosting action because output from solar panel is very less. Dc to high frequency Ac conversion stage is used in order to meet the need of high frequency requirement(50KHz) in induction cooking. The output from the converter is given to an induction coil that produces the electrical energy which is converted to heat due to the resistance of the coil that cooks tahe food very quickly..